Functions
2.4 Backup Overcurrent
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
80
Definite Time Overcurrent Element 50-3
The 50-3 element operates independently of the other elements. Its logic corresponds to the 50-1 and 50-2 el-
ements described above, but operates non-directional only.
If parameter 50-STUB Inrush (address 2653) is set to YES, the element is blocked.
Figure 2-27 Logic diagram of the 50-3 element
Inverse Time Overcurrent Element 51
The logic of the inverse overcurrent element basically operates in the same way as the other elements. The
time delay, however, is calculated based on the type of the set characteristic, the intensity of the current and a
time multiplier (following figure). A pre-selection of the available characteristics was already carried out during
the configuration of the protection functions. Furthermore, an additional constant time delay 51-B AddT-
DELAY or 51N-B AddTdelay may be selected which is added to the inverse time. The possible characteristics
are shown in the Technical Data.
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